Cable clamp

ABSTRACT

A cable clamp ( 10 ) for clamping cable ( 11 ) in a tubular cable feed-through part ( 12 ) that has a pressure piece ( 33 ) comprised of two pressure rings ( 13, 14 ) with a clamping spring ring ( 15 ) positioned between the two pressure rings ( 13, 14 ) to encircle the cable ( 11 ). The pressure rings ( 13, 14 ) are interconnected so that they are movable with respect to each other in an axial direction over a distance permitting the clamping spring ring ( 15 ) to have an inner diameter equal or somewhat greater than the outside diameter of the cable ( 11 ) or compressed so as to have an inner diameter that is less than the outside diameter of cable ( 11 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cable clamp. More particularly, thepresent invention relates to a cable clamp having a clamp lock washerthat is positioned between two thrust collars that are movablyinterconnected so that the lock washer can be pressed against a cable.

2. Description of the Related Technology

A prior art cable clamp is already known from cable glands, for exampleso-called PG cable glands, such as for example the “UNI-Dicht[UNI-Tight] system from Pflitsch that is shown in FIG. 4.

Here the two pressure disks l, the clamp lock washer 2 and the gasket 3are separate parts which must be placed in the cable penetration part 4with a sleeve 5 for installation of the cable clamp in an complex andexpensive manner. Moreover the warehousing and mainly the keeping ofthese separate parts are expensive on site and not always reliablyensured especially for cable connections.

SUMMARY OF THE INVENTION

The object of the invention is to develop a cable clamp of the initiallymentioned type, that is as simple and economical as possible, such thatsimple and prompt installation and economical storage of parts areenabled and the probability is minimized that parts of the cable clampwould be lost or lacking at the installation site.

This object is achieved by providing a movably interconnected pair ofthrust collars having an enclosed clamp lock washer to form a thrustpiece. The thrust piece which consists of two thrust collars and theclamp lock washer and which is assembled beforehand at the manufacturerto simplify both storage and installation and to make cable connectionvery fast. To do this simply the thrust piece can be inserted into thecable penetration part which is generally made as a socket piece of ahousing, the cable can be guided through the sleeve and the relievedthrust piece and finally the sleeve can be attached to the cablepenetration part, all in succession.

In the latter installation step moreover the two thrust collars withtheir permissible axial travel can be pressed against one another, bywhich the clamp lock washer on the oblique inner end faces of the thrustcollars is pressed along the entire periphery towards the axis and thusagainst the cable so strongly that it is fixed by the desired degree.

According to one feature of the invention, the thrust collars are madeby having one of the thrust collars have an annular flange with aninside diameter comparable to the outside diameter of the clamp lockwasher in an uncompressed state. By this feature, without additionalcosts the clamp lock washer is retained and it cannot be laterallydeflected, but is held centrally between the two thrust collars and thusalso uniformly adjoins the cable periphery and can be pressed against itwith a pressure which is the same over the entire contact surface. Thisis not only advantageous when the clamp lock washer is pressed into theplastic jacket of the cable by not doing damage to the jacket, but also,when making electrical contact under pressure it adjoins the shield ofthe stripped shielded cable because then the maximum contact surface isensured.

Another object of the invention has a thrust piece which can be producedeasily and economically, in which the two thrust collars which areprovided for example by an injection molding process without additionalcost so that one thrust collar has a groove and the other a series ofcatch arms. Then after insertion of the clamp lock washer between thethrust collars, they be pushed together. Here the width of the groove issuch that after subtracting the thickness of the catch arms the desiredsize of the axial stoke necessary to compress and relieve the clamp lockwasher results.

The aforementioned insertion-withdrawal process is greatly facilitatedby the catch projections extending from one thrust collar being made toelastically fit into a groove included about the other thrust collar.The one thrust collar then need only be clipped with its catchprojections by a minimum expenditure of force into the groove of theother thrust collar. This installation process if necessary can becarried out without tools by hand. For mechanical production, verysimple tools can be used for this purpose.

One advantageous embodiment of the groove wall behind which the catchprojections fit is to have a conically tapered projection. With thisconstruction an especially small diameter for the thrust pieceprojection is enabled. In addition, over its entire length it has aconstant diameter and thus optimum guidance in the cable penetrationpart.

For the case of a cable gland which is common in practice for shieldedcables the cable shield can be conductively connected to the groundpotential, for example by a metal housing. In the cable clamp of thepresent invention this is done in an advantageously simple manner by atleast one of the two thrust collars consisting of electricallyconductive material. If the housing-side inner thrust collar is made ofmetal, conductive connection of the cable shield takes place via theclamp lock washer and this inner thrust collar lies on the stop collarof the metal cable penetration part. The alternative possibility ofmaking the outer thrust collar of metal for conductive connection of thecable shield to the housing presupposes that the sleeve likewiseconsists of metal and is conductively connected to the outer thrustcollar.

In most applications the cable clamp in a cable penetration part mustmoreover ensure the tightness of the cable connection. This is achievedfor the present invention in the known manner by the arrangement of agasket between the outer thrust collar and the sleeve which when thesleeve is attached to the cable penetration part they are squeezedtogether such that the gasket moreover adjoins the cable and the innersurface of the sleeve under pressure.

This known gasket is a separate part which must be purchased in additionand stored at the warehouse. It is often not ready at the installationsite nonetheless and requires another installation step.

Conversely, in another embodiment of the present invention, especiallyfavorable storage and very simple installation processes for the thrustpiece are achieved by the gasket being mechanically retained in thethrust collar which faces it. In this compact initial version of thethrust piece the connection, for example by screwing or locking, can bedetachable. But the connection can also be nondetachable and thus madecaptive, for example by cementing the gasket to the outer thrust collaror by injection molding it thereto. This second alternative has theadvantage of stronger connection of the gasket to the thrust piece andmore economical production because the thrust collar and the gasketwhich had been injection molded can be produced in a single step bymeans of a double injection mold.

If the elasticity of the material of this thrust collar which faces thecable insertion area of the sleeve is large enough for sealing purposes,but still small enough to be able to accommodate the required pressureof the clamp lock washer when the sleeve is attached to the cablepenetration part, it is especially advantageous to use the thrust collarmoreover as a gasket. Thus a special gasket—whether as a separate partor one connected to the external thrust collar—is no longer necessary,so that the cable clamp can be produced and used especially easily andeconomically.

The greatest possible compactness of the cable clamp of the presentinvention is achieved by the version (see FIG. 1) in which a singlepremounted part is made available to the user by simply clipping thesleeve onto the gasket, which part can be produced not only with minimumcost, but enables extremely uncomplicated handling in practical use.This is because only the (optionally stripped) cable can be insertedthrough the gasket and the thrust piece as far as the desired positionand then the sleeve can be attached to the contact penetration part.Here moreover the cable is clamped securely and the cable penetrationarea is sealed by compressing the gasket liquid-tight.

One especially feasible attachment of the sleeve to the contactpenetration part, for example a socket piece of a housing, consists inproviding a screw sleeve which can be screwed onto the cable penetrationpart which is made as a threaded socket. Not only the desired clampingpressure of the clamp lock washer and thus the necessary tension aboutthe cable is achieved, but also the required sealing action according tothe requirements of the individual case is achieved by the intensity oftightening of the screw sleeve in conjunction with the material selectedfor the gasket and the axial dimensions of the interacting parts of thecable clamp.

A simple and economical possibility for electrically insulating themetallic housing together with the socket piece and at the same timeprotecting it mechanically is to have a peripheral plastic molded sleevepositioned about the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained below using one embodiment in the figures.

FIG. 1 shows an axial section through are installed cable clamp of thepresent invention, which has not yet been completely attached to thecable insertion connecting piece;

FIG. 2 shows an exploded axial section through the individual parts ofthe cable clamp of the present invention;

FIG. 3 shows an overhead view of the end faces of the two thrust collarsfacing one another and the clamp lock washer; and,

FIG. 4 shows a halved view of a cable gland known from the prior art.

DETAILED DESCRIPTION OF THE INVENTION

A cable clamp 10 (see FIG. 2) for clamping a shielded cable 11 in atubular cable insertion connecting piece 12 of a metal housing which isnot shown and which is integral with it for holding an electricalcircuit is shown in FIG. 1. The cable clamp 10 consists of ahousing-side inner metal thrust collar 13, a cable-side outer thrustcollar 14 of plastic, a clamp lock washer 15 which is located betweenthem and which is bent from a helical metal spring, a gasket 17 which isinjection-molded to the cable-side end face 16 of the outer thrustcollar 14, and a screw sleeve 18 which encompasses the gasket and whichcan be screwed onto a matched external thread 19 of the cable insertionconnecting piece 12.

The insertion connecting piece 12 consists of a metallic inner socketpiece 20 which is made in one piece with the metal housing, and atubular plastic jacket 21 which is produced by extrusion coating andwhich has an external thread 19 on its free end. The screw sleeve 18 hasa knurled grip 22 by which the required torque can also be applied whenscrewing on by hand.

The gasket 17 has a collar 23 with a peripheral recess 24 into which aterminal shoulder 25 of the screw sleeve 18 fits such that it can beturned on the one hand relative to the gasket 17 and on the other handwhen screwed onto the external thread 10 compresses the gasket 17. Indoing so the screw sleeve 18 and gasket 17 adjoin one another over alarge surface by corresponding shaping of their surfaces facing oneanother such that high pressure is transferred both in the axial andalso in the radial direction. The contours 26, 27 of the surfaces of thescrew sleeve 18 and the gasket 17 which are pressed against one anotherfor this purposes are arched concavely or correspondingly convexly, bywhich on the one hand the indicated force transfer is produced as in theinteracting conical surfaces and on the other hand the gasket 17 isprevented from sliding through the inlet opening 28 of the screw sleeve18.

Due to pressure in the radial direction the gasket 17 is moreoverpressed against the inner surface 26 of the screw sleeve 18 and over alarge area against the cable surface so that the cable insertion area ofthe cable insertion connecting piece 12 is reliably sealed. In addition,the gasket 17 is also pressed against the inner wall 29 of the free endpart of the plastic sleeve 21, by which the cable clamp 10 is alsosecured against penetration of liquid via the threaded gland.

The end faces 30, 31 of the two thrust collars 13, 14 facing one anotherare tapered conically towards the axis A of the cable clamp 10. The endface 30 of the inner thrust collar 13 has on the outer edge an axiallyprojecting end flange 32 which prevents lateral divergence of the clamplock washer 15 which in the relieved state adjoins its inner surface andthus the installation of the thrust piece 33 which consists of thethrust collars 13, 14, and the clamp lock washer 15 is greatlyfacilitated in a simple manner.

The inner thrust collar 13 has a peripheral groove 34 with a firstgroove wall 35 facing the clamp lock washer 15 and a second groove wall36.

The outer thrust collar 14 bears six catch arms 37 which are integraltherewith, which are distributed uniformly on the periphery and whichare provided with catch projections 38 which project towards the axis A,which are located on the free ends, and which each have an insertionbevel 39. The first groove wall 35 is equipped with an leading bevel 40which corresponds to the insertion bevel 39.

With the thrust piece 33 installed the catch projections 38 fit behindthe first groove wall 35 and can be moved axially by a correspondinglychosen width of the peripheral groove 34 [in it] by a stroke which issufficient to compress the clamp lock washer 15. With the screw sleeve18 strongly screwed on the required clamping force is achieved forapplying tension to the cable 11.

The diameter of the first groove wall 35 is less by than the materialthickness of the catch arm 37 and less than that of the second groovewall 36 so that the thrust piece 33 over its entire length has aconstant outside diameter and thus can be inserted unhindered into thecable insertion connecting piece.

In the production of the cable clamp 10, first of all the thrust piece33 is produced. To do this only the clamp lock washer 15 need beinserted into the inner thrust collar 13 and the outer thrust collar 14with the gasket 17 molded on its outer end face 16. Then the outerthrust collar 14 can be clipped onto the inner thrust collar 13. Thiscan also be done by hand because the corresponding oblique surfaces 39,40 require a low expenditure of force. Afterwards only the screw sleeve18 need be guided over the gasket 17, with its terminal shoulder 25engaged in the peripheral recess 24 of the gasket 17.

In this state the tension of clamp lock washer 15 is relieved and itadjoins on the outside the end flange 32 of the inner thrust collar 13.The catch projections 38 adjoin the first groove wall and the insidediameter of the clamp lock washer 15 is slightly larger than the outsidediameter of the cable shield 41 which is to be clamped.

For the user this preinstalled cable clamp 10 can be easily stored andinstalled at the installation site, the uncertainty of a missingindividual part being eliminated.

For installation, the cable clamp 10 can be pushed simply into the cableinsertion connecting piece 12 as far as a stop of the housing-sideexternal end face 42 of the inner thrust collar 13 on the face edge 43of the inner socket piece 20, then the correspondingly stripped cable 11can be inserted through the gasket 17 and the clamp lock washer 15 sofar that the cable shield 41 is positioned at the height of the clamplock washer 15 and then the screw sleeve 18 can be screwed securely onthe external thread 19 of the plastic sleeve 21 of the cable insertionconnecting piece 12. In this final installation step the gasket 17 ispressed over a large area under pressure against the cable jacket 44,the inner surface 26 of the screw sleeve 18 and the inner surface of theplastic sleeve 20 and moreover the outer thrust collar 14 is pressedagainst the inner thrust collar 13, the clamp lock washer 15 on itsconical surfaces 30, 31 radially sliding centrally towards the axis Aand in doing so being pressed into the cable shield 41 until the catcharm 37 adjoins the second groove wall 36 of the peripheral groove 34 ofthe inner thrust collar 13. This stroke is such that a sufficiently highclamping force is achieved and thus the required tension about the cable11 is ensured and [that] on the other hand there is no undue deformationof the cable shield 41.

The described cable clamp 10 is therefore extremely simple andeconomical in production and handling, thus ensuring effective tensionabout the cable 11, high liquid-tightness and permanently securingcontact between the cable shield 41 and the metal housing, which takesplace via the clamp lock washer 15, the metal inner thrust collar 13 andthe conductive inner socket piece 20.

What is claimed is:
 1. A cable clamp for clamping a cable comprising: aclamp lock washer; a first thrust collar having a first outer end faceand a first inner end face, and a second thrust collar having a secondinner end face; at least two catch arms disposed from said second thrustcollar that are interconnected with said first thrust collar, said catcharms being disposed to permit said first and second thrust collars to bemoved closer together and further apart from each other along a linearpath having a restricted fixed distance length, said clamp lock washerbeing disposed between said first and second inner end faces, and,distances between said first and second inner end faces increasingtoward a central axis of the interconnected first and second thrustcollars; a tubular cable penetration part having a stop shoulder locatedon an inner wall of said cable penetration part with said first outerend face of said first thrust collar disposed adjacent said stopshoulder; and a sleeve adjustably attached to said cable penetrationpart for movement of said sleeve to move said second thrust collartoward said first thrust collar to compress said clamp lock washer toabut against said cable.
 2. The cable clamp of claim 1, wherein saidfirst thrust collar has an annular flange disposed from said first innerend face, and said annual flange has an inside diameter that correspondsto an outside diameter of said clamp lock washer in a relieved state. 3.The cable clamp of claim 1, wherein at least one of said first or secondthrust collars is made of an electrically conductive material.
 4. Thecable clamp of claim 1, further comprising a gasket disposed betweensaid sleeve and a second outer end face of said second thrust collar. 5.The cable clamp of claim 4, wherein said gasket is cemented to saidsecond outer end face.
 6. The cable clamp of claim 4, wherein saidgasket is injection molded to said second outer end face.
 7. The cableclamp of claim 4, wherein said gasket is integral with said second outerend face.
 8. The cable clamp of claim 4, wherein said sleeve includes aterminal shoulder and said gasket includes a recess into which saidterminal shoulder is disposed.
 9. The cable clamp of claim 4, whereinsaid gasket is made of a compressible material.
 10. The cable clamp ofclaim 1, wherein said sleeve includes internal threads that mate withexternal threads disposed about said cable penetration part.
 11. Thecable clamp of claim 1, wherein said cable penetration part includes atubular socket of a housing in which said cable is connected toelectrical circuit parts.
 12. The cable clamp of claim 11, wherein saidcable penetration part includes a plastic molded sleeve disposed aboutsaid socket.
 13. A cable clamp for clamping a cable comprising: a clamplock washer; a first thrust collar having a first outer end face and afirst inner end face, and a second thrust collar having a second innerend face; at least two catch arms disposed from said second thrustcollar that are interconnected with said first thrust collar, said catcharms being disposed to permit said first and second thrust collars to bemoved closer together and further apart from each other along a linearpath having a restricted fixed distance length, said clamp lock washerbeing disposed between said first and second inner end faces, and,distances between said first and second inner end faces increasingtoward a central axis of the interconnected first and second thrustcollars; a tubular cable penetration part having a stop shoulder locatedon an inner wall of said cable penetration part with said first outerend face of said first thrust collar disposed adjacent said stopshoulder; and a sleeve adjustably attached to said cable penetrationpart for movement of said sleeve to move said second thrust collartoward said first thrust collar to compress said clamp lock washer toabut against said cable wherein said first thrust collar has aperipheral groove disposed about an outside diameter that is indentedtoward a central axis of said first thrust collar, and said secondthrust collar has said catch arms disposed about a peripheral region.14. The cable clamp of claim 13, wherein each of said catch arms has acatch projection that projects radially toward a central axis of saidsecond thrust collar, said catch projections being adapted toelastically fit over and behind a first wall projecting out from saidperipheral groove of said first thrust collar.
 15. The cable clamp ofclaim 14, wherein said catch projections are tapered conically towardthe central axis of said second thrust collar.
 16. The cable clamp ofclaim 14, wherein said first wall projects away from said peripheralgroove by a distance that is less than that of a second wall alsoprojecting away out from said peripheral groove.
 17. The cable clamp ofclaim 16, wherein said first wall projects out from said peripheralgroove by a distance equal to a distance said catch projections projectradially from said catch arms toward the central axis of said secondthrust collar.
 18. A method for clamping a cable comprising: providing aclamp lock washer; providing (i) a first thrust collar having a firstouter end face and a first inner end face, and (ii) a second thrustcollar having a second inner end face; positioning said clamp lockwasher between said first and second inner faces; interconnecting saidfirst and second thrust collars to permit said first and second thrustcollars to be moved closer together and further apart from each otheralong a central axis of the interconnected said first and second thrustcollars, this movement being along a linear path having a restrictedfixed distance length, said clamp lock washer being retained between theinterconnected said first and second inner faces; providing a tubularcable penetration part having a stop shoulder located on an inner wallof said cable penetration part; positioning said first outer end face ofsaid first thrust collar adjacent said stop shoulder; providing a sleevemovably attached to said cable penetration part; and moving said sleevewith respect to said cable penetration part to move said second thrustcollar closer to said first thrust collar to compress said clamp lockwasher to abut against said cable.
 19. A cable clamp for clamping acable comprising: a clamp lock washer; a first thrust collar having afirst outer end face and a first inner end face, and a second thrustcollar having a second inner end face; at least two catch arms disposedfrom said first thrust collar that are interconnected with said secondthrust collar, said catch arms being disposed to permit said first andsecond thrust collars to be moved closer together and further apart fromeach other along a linear path having a restricted fixed distancelength, said lock washer being disposed between said first and secondinner end faces, and distances between said first and second inner endfaces increasing toward a central axis of the interconnected first andsecond trust collars; a tubular cable penetration having a stop shoulderlocated on an inner wall of said cable penetration part with said firstouter end face of said first thrust collar disposed adjacent said stopshoulder; and a sleeve adjustably attached to said cable penetrationpart for movement of said sleeve to move said second thrust collartoward said first thrust collar to compress said clamp lock washer toabut against said cable.
 20. The cable clamp of claim 19, wherein saidsecond thrust collar has an annular flange disposed from said firstinner end face, and said annual flange has an inside diameter thatcorresponds to an outside diameter of said clamp lock washer in arelieved state.
 21. The cable clamp of claim 19, wherein at least one ofsaid first or second thrust collars is made of an electricallyconductive material.
 22. The cable clamp of claim 19, further comprisinga gasket disposed between said sleeve and a second outer end face ofsaid second thrust collar.
 23. The cable clamp of claim 22, wherein saidgasket is cemented to said second outer end face.
 24. The cable clamp ofclaim 22, wherein said gasket is injection molded to said second outerend face.
 25. The cable clamp of claim 22, wherein said gasket isintegral with said second outer end face.
 26. The cable clamp of claim22, wherein said sleeve includes a terminal shoulder and said gasketincludes a recess into which said terminal shoulder is disposed.
 27. Acable clamp for clamping a cable comprising: a clamp lock washer; afirst thrust collar having a first outer end face and a first inner endface, and a second thrust collar having a second inner end face; atleast two catch arms disposed from said first thrust collar that areinterconnected with said second thrust collar, said catch arms beingdisposed to permit said first and second thrust collars to be movedcloser together and further apart from each other along a linear pathhaving a restricted fixed distance length, said lock washer beingdisposed between said first and second inner end faces, and distancesbetween said first and second inner end faces increasing toward acentral axis of the interconnected first and second trust collars; atubular cable penetration having a stop shoulder located on an innerwall of said cable penetration part with said first outer end face ofsaid first thrust collar disposed adjacent said stop shoulder; and asleeve adjustably attached to said cable penetration part for movementof said sleeve to move said second thrust collar toward said firstthrust collar to compress said clamp lock washer to abut against saidcable wherein said second thrust collar has a peripheral groove disposedabout an outside diameter that is indented toward a central axis of saidsecond thrust collar, and said first thrust collar has said catch armsdisposed about a peripheral region.
 28. The cable clamp of claim 27,wherein each of said catch arms has a catch projection that projectsradially toward a central axis of said first thrust collar, said catchprojections being adapted to elastically fit over and behind a firstwall projecting out from said peripheral groove of said second thrustcollar.
 29. The cable clamp of claim 28, wherein said catch projectionsare tapered conically toward the central axis of said first thrustcollar.
 30. The cable clamp of claim 28, wherein said first wallprojects away from said peripheral groove by a distance that is lessthan that of a second wall also projecting away out from said peripheralgroove.
 31. The cable clamp of claim 30, wherein said first wallprojects out from said peripheral groove by a distance equal to adistance said catch projections project radially from said catch armstoward the central axis of said first thrust collar.
 32. The cable clampof claim 22, wherein said gasket is made of a compressible material. 33.The cable clamp of claim 19, wherein said sleeve includes internalthreads that mate with external threads disposed about said cablepenetration part.
 34. The cable clamp of claim 19, wherein said cablepenetration part includes a tubular socket of a housing in which saidcable is connected to electrical circuit parts.
 35. The cable clamp ofclaim 34, wherein said cable penetration part includes a plastic moldedsleeve disposed about said socket.